It uses third party (community-provided) relay servers: https://docs.syncthing.net/users/strelaysrv.html https://docs.syncthing.net/users/strelaysrv.html This

It uses third party (community-provided) relay servers: https://docs.syncthing.net/users/strelaysrv.html https://docs.syncthing.net/users/strelaysrv.html This can have quite an effect on sync speed. I set it up for my dad and initially his PC and laptop were syncing incredibly slowly. It turned out they both thought his home network was a public one, so everything was going out to a relay server and back.